The proposed research encompasses two areas of investigation, both of which utilize the goldfish Mauthner cell (M-cell) as a model. In the first aspect, properties of the following identified synapses will be studied with simultaneous intracellular recordings from pre- and post synaptic elements: 1) inhibitory synapse between identified interneurons and the M-cell. Emphasis will be placed upon analysis of mechanisms of transmitter release and synaptic transfer functions. Also, the patterns of M-cell collateral and sensory inputs to the inhibitory interneurons will be determined in order to develop a model of interneuron function. The second aspect deals with the axon reaction of central neurons. Intra- and extracellular recordings will be used to determine alterations in M-cell membrane properties and synaptic interactions produced by spinal cord transection and M-cell deafferentation. These studies will be correlated with morphological investigations at the light and electron microscopic levels. Finally, the role of inter- and intraneuronal trophic interactions in the maintenance and regulation of M-cell membrane properties and synaptic transmission will be studied. These investigations will involve the intracellular injection of labeled amino acids, nucleoside derivatives, glycoproteins and mucopolysaccharides, with emphasis placed on an analysis of dendritic transport functions. These systems will also be investigated after axotomy and intracellular injections of colchicine in order to correlate the trophic functions with neuronal and trans-neuronal responses to injury. BIBLIOGRAPHIC REFERENCES: Ethanol suppresses collateral inhibition of the goldfish Mauthner cell. Brain Res. 104 (1976) 347-353. (Faber, D.S. and Klee, M.R.). Action of ethanol on neuronal membrane properties and synaptic transmission. In: Alcohol and Opiates: Neurochemical and Behavioral Mechanisms. Ed. K. Blum, Academic Press, N.Y., 1977, pp. 41-64 (Faber, D.S. and Klee, M.R.).